1. Field of the Invention
The present invention relates to the design of a bipolar cell for gas depolarized rechargeable batteries such as nickel hydrogen and zinc oxygen.
2. Discussion of the Prior Art
A vexing problem with bipolar batteries is the need for an electrolyte seal between individual cells to prevent battery short circuits. This problem is exacerbated in batteries with a gas phase active material as communication to a common gas storage space must be provided. Thus both a liquid seal and a gas vent are required.
An additional problem with these batteries is that means must be found to prevent gas phase water transfer between cells either as water vapor or as a result of parasitic reactions which generate oxygen in the case of a nickel hydrogen battery or hydrogen in the case of a zinc oxygen battery. If the parasitic gases are transported to the bulk vapor space then they may preferentially recombine with the depolarizing gas in those cells closest to the gas space. For example, O.sub.2 generated during nickel electrode overcharge in a nickel hydrogen cell may react with hydrogen within the cell or be transported out of the cell and react in the gas storage vessel or in another electrode. O.sub.2 lost from the cell may be converted to H.sub.2 O in other cells or other parts of the battery. This leads to "dry out" and failure of the cell from which O.sub.2 is lost.